Sending a message to an instance method from inside a block - objective-c

Question

I am relatively new to Cocoa programming. Basically, I want to send a message within a method in my Document class to an intense of a class (that inherits from NSView) that I have initialised as a property in the #interface of the Document class.
Here is the simplified version:
///////////////////////////KOZDocument.h///////////////////////////
#import <Cocoa/Cocoa.h>
#import "KOZOtherClass.h"
#interface KOZDocument : NSDocument
#property (assign) IBOutlet KOZOtherClass *otherClassInstance; //this would be connected to the relevant CustomView in the IB
#end
///////////////////////////KOZDocument.m///////////////////////////
#import "KOZDocument.h"
#implementation KOZDocument
- (id)init
{
self = [super init];
if (self) {
// I want to send a message to otherClassInstance from some method e.g. init
NSLog(#"INITIALISING");
[[self otherClassInstance] printMessage];// this is the message I want to work but which doesn't (even though i don't any errors)
//sending the message to a locally initiated instance works but I don't want to use a local instance because i want to connect it to a CustomView in IB
KOZOtherClass *otherClassLocalInstance = [[KOZOtherClass alloc] init];
[otherClassLocalInstance printMessage];
}
return self;
}
//.….
///////////////////////////KOZOtherClass.h///////////////////////////
#import <Foundation/Foundation.h>
#interface KOZOtherClass : NSView
- (void) printMessage;
#end
///////////////////////////KOZOtherClass.m///////////////////////////
#import "KOZOtherClass.h"
#implementation KOZOtherClass
- (void) printMessage{
NSLog(#"This method can be called!!");
}
#end
/////////////////////////////////////////////////////////////////////
The same methodology works for all the native Cocoa objects but not for mine.
Can anyone tell me what I'm doing wrong?
Here is the context of why i want to do this:
I am building an app that plays a video using the AVFoundation. I have an animation I want to trigger in an NSView when the playback reaches a particular part in the video (e.g. after 2 seconds). I am adapting Apple's AVSimplePlayer and using the time observer to get the position of the playhead. The time observer executes the code inside a block for every given time interval. In this block I want to send a message to my animation view to trigger the animation when the time is more that 5 seconds for example.

Answer 1

In -init of your objects the Interface Builder connections are not set yet, the loading mechanism can't set those before your object is initialized.
Instead you want to overwrite the -awakeFromNib method like so:
- (void)awakeFromNib {
[[self otherClassInstance] printMessage];
}
-awakeFromNib is guaranteed to be called after the connections have been made. Depending on the exact implementation you may also need to guard against that code being executed twice, for example by having a boolean instance variable didWake that you check/set in that method.